Add necessary files to train DeepPixBis

bob/learn/tensorflow/losses/__init__.py

+# fmt: off
+from .balanced_cross_entropy import \
+    balanced_sigmoid_cross_entropy_loss_weights  # noqa: F401
+from .balanced_cross_entropy import \
+    balanced_softmax_cross_entropy_loss_weights  # noqa: F401
+# fmt: on
 from .center_loss import CenterLoss
 from .center_loss import CenterLossLayer
+from .pixel_wise import PixelwiseBinaryCrossentropy
 
 
 # gets sphinx autodoc done right - don't remove it
@@ -18,5 +25,5 @@ def __appropriate__(*args):
         obj.__module__ = __name__
 
 
-__appropriate__(CenterLoss, CenterLossLayer)
+__appropriate__(CenterLoss, CenterLossLayer, PixelwiseBinaryCrossentropy)
 __all__ = [_ for _ in dir() if not _.startswith("_")]